An amplifier is utilized in various applications of remote sensing and communication equipment. Applications of the amplifier include radar, ultrasound, wireless communication and even speech analysis. These applications use the amplifier to enhance dynamic performance. An amplifier is categorized as low noise amplifier (LNA), variable gain amplifier (VGA) and programmable gain amplifier (PGA). Each of these amplifiers is used to sense and amplify low level signals.
The low noise amplifiers (LNAs) are used in receivers to amplify radio frequency (RF) signals received by a receive antenna. LNAs which are required to present a high input impedance have a V2I (voltage to current) architecture followed by an I2V (current to voltage) architecture. A bandwidth programmability of the LNA is incorporated into the I2V architecture.
The I2V architecture includes load resistors, a set of switches and a set of capacitors. When the LNA is used in a differential mode, the set of switches used in the I2V architecture invariably see a large voltage swing which degrades linearity of the LNA. In addition, the unused capacitors in the set of capacitors have to be biased to a voltage through a large resistor which introduces slow settling components in the LNA.